1. Field of the Invention
This invention relates to measuring the level and specific gravity of fluid within a tank or vessel. More particularly, the present invention relates to using multiple different buoyancy load sensors placed within a tank or vessel that is filled with fluid. The multiple different buoyancy load sensors are each made of different density or cross sectional to cancel out any accumulation of contamination that may collect on the buoyancy elements placed within the fluid. The buoyancy elements can be fabricated in pieces that can be placed within the tank in pieces to make a longer sensing element. Different buoyancy characteristics allow identification of the specific gravity of the fluid based upon the different forces on the buoyancy elements.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98:
Several products have been patented to measure the amount of fluid within a tank. For most of these patents, the tank is pressurized and may be filled with a fluid that may minimally collect of the load-sensing element placed within the tank. The accumulation of material on the element changes the reading on the amount of fluid within the tank.
Legendre et al. U.S. Pat. No. 5,641,672 discloses an apparatus for measuring the liquid contents of a tank where the tank is pressurized. This patent uses a single buoyancy element to measure the amount of fluid within a tank. The tank is also closed and sealed to maintain pressure within the tank. Any accumulation of debris on the buoyancy element will cause false reading. The buoyancy element is hung free from the sensor and movement of fluid within the tank can cause false readings. This patent further assumes the shape of the tank is linear and that the cross sectional area of the tank does not change based upon the level of fluid within the tank. The accuracy of this measurement is based upon a known specific gravity of the material within the tank. If the density changes then the accuracy of the amount of fluid within the tank is inaccurate.
Kemp U.S. Pat. No. 6,202,486 discloses an analog liquid level sensor. This sensor uses two thermocouples and a resistance wire to measure the amount of fluid within the tank. The sensors measure the difference in temperature between the two sensors to determine the amount of fluid within the tank. This patent requires that one sensor be placed above the fluid level and a second sensor placed below the fluid level, and may not accommodate where the fluid level goes above or below the two sensors. The sensors are placed on a single pole, and cannot be expanded to different lengths. Turbulent flow of fluid within the tank may further change the reading on the amount of fluid within the tank. This patent further assumes the shape of the tank is linear and that the cross sectional area of the tank does not change based upon the level of fluid within the tank.
Scott et al. U.S. Pat. No. 6,834,544, U.S. Patent Application 2003/0221482 and U.S. Patent Application 2004/0050157, discloses a liquid volume monitor for pressurized tanks. This patent uses a single suspended buoyancy element attached to a sensor with multiple temperature sensors to calculate the volume in the tank. The patent is more specifically written for hazardous or flammable materials where the density of the fluid changes based upon temperature. The tank is also closed and sealed to maintain pressure within the tank. Any accumulation of debris on the buoyancy element will cause false reading. The buoyancy element is hung free from the sensor and movement of fluid within the tank can cause false readings. This patent further assumes the shape of the tank is nearly cylindrical and that the cross sectional area of the tank does not change significantly based upon the level of fluid within the tank. The temperature sensor helps to minimize erroneous readings when the specific gravity of the fluid within the tank changes as a result of temperature changes. Contaminants within the tank can also cause changes in the specific gravity and the temperature sensors can't detect these differences.
What is needed is a tank volume measurement device that uses multiple cross-sectional or density elements that can cancel out any accumulation of debris or contamination of the buoyancy elements. The ideal device would further be able to accommodate tanks of varying cross-sections, and include at least one temperature sensor to account for fluid density changes based upon temperature or based upon ambient temperature sensor variations. The two separate sensors also are useful to determine changes in the specific gravity of the fluid. The proposed application satisfies these requirements.